Imagine if SPN was a Marvel movie and at the end of each season finale you would get to watch the famous 'post credits' scene. This is what should have happened in three short shots before the end credits of season 10 to hint at season 11:
The scene begins with this shot; hell slowly coming into view. The camera carefully moves down the hallway, tilting left and right in order to see the people chained to the walls. All is silent apart from the screams of inmates and clanking chains. There's the occasional flash of red lights from above - the camera stops.
The camera is now facing a long hallway, different from the one from which it came. It's much darker and as the camera moves down it, the screams get quieter and quieter until they are muffled to silence. The flickering red lights continue as the viewer is faced with a heavily bolted door covered in symbols. Suddenly, the door cracks and the chains and symbols crumble, becoming dust as the door creaks open. Once fully open, there is nothing but darkness.
The camera is now slightly unfocused as a figure emerges from the door. Though hazy, it can be clearly seen the figure is male and wearing a white suit whilst carrying a rose. As the camera sharpens, you can see the man smile as he says
"Six years is close enough..."
The camera now suddenly becomes engulfed in 'The Darkness', the sound of it encasing the scene completely. Laughter is heard. The Supernatural credits roll.